The instant invention relates to a gear transmission, and particularly to a gear transmission for textile machines.
Gear transmissions utilizing belt drives wherein the transmission ratio can be varied are known from the state of the art. These devices are controlled by varying the belt tension or by excursion of the belt at a right angle to the running direction, causing a belt disk of the gear transmission which is in form of a spring washer to change its active diameter for the belt. Such gear transmissions can find many different applications because the transmission ratio of the gear transmission can thus be changed easily and continuously within certain limits. Such gear transmissions have, however, the disadvantage that the transmission ratio changes in the course of operation due to belt wear. Thus, control rectification becomes necessary if a given transmission ratio is to be maintained during prolonged use.
The invention is described below through the example of application in textile machines in form of trouble-shooting gear transmission, where it can be used to especially good advantage because particularly great wear occurs due to the constant variation of the transmission ratio and the desired transmission ratio must be safely maintained.
In making conical or cylindrical cross-wound bobbins with so called "wild winding", the problem exists that the yarn is deposited on the bobbin in such a manner that yarn layers wound up one after the other are laid down very closely next to each other or over each other, especially when the ratio of the diameter of the wind-up bobbin and the evolution of the back-and-forth movement of the yarn guide reaches an even number. This so-called ribbon windings can lead to interference in further processing of the bobbins. For example, when the yarn is drawn off, several layers may be drawn of at the same time and this may result in yarn breakage. To avoid this, trouble-shooting devices are used in which a yarn being fed at constant speed to a wind-up device constituting a bobbin is deposited on the bobbin at varying cross-winding speeds. As a consequence, the crossing angle of the yarn changes and ribbon winding is prevented.
DE-OS 23 53 234 discloses a trouble-shooting gear transmission in which two toothed wheels with different numbers of teeth are driven by a shaft, with one of the toothed wheels being provided with an axial cam interacting with a connecting rod that is engaged with a catch on the eccentric that controls the yarn guide. This device has the disadvantage that, in order to change the yarn crossing angle, practically the entire trouble-shooting gear transmission and the yarn guide gear transmission must be changed. A further disadvantage consists in the fact that the variation of the yarn guide speed takes place within a predetermined framework which can only be changed at great cost, and that the variation of the yarn guide speed is not sufficiently great.
A system is known through the rotor spinning machine RU 14 of Schubert Salzer AG Ingolstadt, Germany, in which the rotational speed of the yarn guide gear transmission, and thereby the speed of the back-and-forth yarn guide movement, is varied by an upstream trouble-shooting gear transmission that is in the form of a V-belt gear transmission with a regulating disk. By varying the belt tension, the effective diameter of the regulating disk is varied so that the yarn guide gear transmission is driven at a changed speed. Belt wear can however cause changes in the transmission ratio with this arrangement so that the set mean transmission ratio, and thereby the desired mean crossing angle, changes. Belt wear is not so much expressed in a lengthening of the belts than in a change in their flanks. At the same time, the width of the belts change so that it becomes narrower. As a consequence, the belt dips deeper into the V-belt disk. At the same time belt tension decreases resulting in the regulating disk, in the form of a spring washer, to compensate for the decreasing belt tension. This causes the belts to run on a larger diameter of the spring washer whereby the transmission ratio of the belt drive is changed significantly. The effective diameter of the two belt disks also changes at the same time and with increased effect.